The rise of SSDs over hard drives, debunked

In spite of a recent report to the contrary, solid-state drives (SSDs) will not surpass hard disk drives (HDDs) in either price or capacity any time soon, according to industry analysts.

In fact, hard drives will remain the dominant mass storage device in laptops and desktops for years to come.

For example, a data center-class HDD with 6TB of capacity sells for $US185 today and will drop to about $US165 by the end of the year -- about .3 cents per gigabyte, according to market research firm Gartner. A 4TB HDD for a laptop sells for $95 to computer manufacturers or about .2 cents per gigabyte.

And HDD prices are expected to continue to drop as areal platter density increases. Gartner predicts that over the next five years, HDD prices will drop to as low as .1 of a cent per gigabyte of capacity.

A variety of technologies are allowing HDD prices to continue their steady decline, including perpendicular magnetic recording that stands data bits in an upright, skinnier orientation and helium-filled drives that reduce friction and allow more platters to be squeezed more tightly together.

HDD technologies such as Bit Patterned Media Recording (BPMR) and Heat-Assisted Magnetic Recording (HAMR) will result in up to 10-terabit-per-square-inch (Tbpsi) areal densities by 2025, compared with today's .86 Tbpsi areal densities. Industry roadmaps reveal HDD drives with up to 100TB capacity coming in the next decade.

"SSDs of any grade will still be in the .14 to .17 cent [per gigabyte] range in 2019," said Joseph Unsworth, Gartner's vice president of SSD research, adding that prices for SSDs won't likely match those of HDDs, even by 2025.

As technology allowing more dense NAND flash chips has advanced, SSD prices have plummeted. Today, consumers can pick up SSDs for as little as .38 cents per gigabyte, but that's nowhere near the .9 cents per gigabyte that hard drives generally cost consumers today, according to Gartner.

But price isn't the only consideration when purchasing an SSD. Flash memory is more than twice as fast as spinning disks and it's far more reliable for mobile purposes because there are no moving parts.

If there's one upgrade a consumer can make to a desktop or laptop computer that will make the greatest difference in performance, it's swapping in an SSD.

NAND flash manufacturers such as Samsung, Toshiba, Micron, and Intel, have continued to shrink the lithography technology for making flash transistors. Last fall, at the Flash Memory Summit, Toshiba revealed its smallest lithography process for NAND flash with a 15-nanometer, 16GB MLC NAND wafer. The 15nm wafer was developed in partnership with SanDisk.

Flash makers have also increased the number of bits -- from one to three -- that can be stored per NAND flash cell, all of which has increased density and reduced manufacturing costs.

Today, multi-level cell (MLC, or two bits per cell) and triple-level cell (TLC, or three bits per cell) NAND flash dominates the market.

More recently, the same flash makers have introduced three-dimensional architectures that allow layers of NAND flash to be stacked atop each other like a microscopic skyscraper. Samsung started the trend with a 32-layer chip it called V-NAND. Toshiba then followed with a 48-layer 3D flash memory called BiCS (Bit Cost Scaling).

The result of the technological advances is a 16GB chip that can be used to produce high capacity SSDs that today offer 4TB of capacity for consumers and will likely be knocking on 8TB and 10TB in the near future -- perhaps even by the end of the year.

For example, SanDisk hopes to release an 8TB SSD this year. Manuel Martull, SanDisk's product and solutions marketing director, has said the company hopes to continue doubling SSD capacity every one to two years, vastly outpacing traditional HDD capacity growth.

The advances in NAND flash density that have some writing that SSDs will reach price parity with HDDs, a claim that experts balk at.

Of all the NAND flash makers, only Micron and Intel have publicly discussed a 32GB (3D MLC) and 48GB (3D TLC) chip, both of which are 32 layers deep. But even that memory would not be 32 or 64 times the capacity todays NAND flash dies. Even a 128GB single die (1Tbit) chip would only be eight times the density increase over today's chips, according to Gartner.

"There's a stupefying quantity of hogwash out there," said John Monroe, vice president of research for data center systems at Gartner. "HDD makers are forecasting a 20TB HDD...in 2020; my guess is the [manufacturer] cost would be around $US175 per drive.

"In 2020, let's assume a cost of $US0.11/GB for a 25TB SSD, that would be $2,750 manufacturer cost per drive," Monroe added.

And, when it comes to data center class SSDs, on average the price per gigabyte of capacity is still nine times higher than HDDs, according to Fang Zhang, a senior storage analyst at IHS research.

"I would agree that SSD vendors will eventually be able to cram more capacity per form factor [than hard disk drives] but this is not the same as price per gigabyte," Zhang wrote in an email reply to Computerworld.

SSDs are, however, expected to dominate HDDs in laptops and desktops, but that isn't expected to happen for years. At the end of last year, SSDs were only in about 15 per cent of new notebooks. By 2019, SSDs are expected to be in about 56 per cent of notebooks and desktops. Around that same time, SSDs will cost computer makers about $US45 for a 256GB drive, according to Unsworth.

"That's when the market will see some major shifts," Unsworth said in an email reply to Computerworld.

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